1. Field of the Invention
This invention pertains generally to gas flow surge suppressors and safety shut-off valves and more particularly to a combination surge suppressor and safety shut-off valve that preferably allows for automatic restoration of nominal fluid flow, a reset, after engagement of the safety shut-off valve.
2. Description of the Background Art
Catastrophic events, such as earthquakes, floods or similar events, can compromise distribution systems, such as the rupture of pipelines carrying liquids or gasses to residential and commercial structures. The typical liquids and gases being distributed for residential use are water, and combustible substances, which may comprise combustible gasses (i.e. hydrocarbons such as methane, pentane, or natural gas), or combustible liquids (i.e. fuel oil, gasoline, diesel fuel, and so forth). It will be appreciated, however, that pipelines may carry any number of liquid or gaseous substances, such as for distribution within an industrial plant.
The rupture of water pipelines caused by a catastrophic event (natural or man made) may result in additional damage being wrought on structures and property. However, it will be appreciated that when the substance being distributed is volatile, or otherwise poses a danger to persons and property, the damage caused by a rupture may be increased by orders of magnitude. For example, the fluidic substance may comprise combustible, corrosive, poisonous, radioactive, or similarly potentially dangerous substances. The majority of dangerous pipeline ruptures occur in pipelines carrying combustible substances, such as hydrocarbon gases, which can rupture to create a substantial risk of explosion or asphyxiation. In addition, ruptures in pipes carrying combustible substances can pose a significant danger to emergency and rescue personnel as well as others.
The safety of any system which distributes fluidic substances, either gaseous or liquid form, can be enhanced by the placement of shut-off valves (also referred to as cut-off valves, safety valves, surge relief valves, and so forth) at appropriate locations in the distribution system that will automatically shut off the flow of the fluidic substance when a downstream rupture occurs in the system. Additionally, in a residential setting, the shut-off valve is typically placed on the low-pressure end of a regulator unit that is attached to the gas source, such as a pressure regulating associated with a gas meter. The shut-off valve serves to interrupt the flow of gas in the event of regulator failure, or if a catastrophic failure in the downstream portion of the distribution system occurs, such as a rupture.
In addition, surge conditions arise in fluid distribution systems that may disrupt associated equipment or create increased risk of injury or property damage. For example, consider a natural gas distribution pipeline that connects to a stove having a pilot light. Surges in gas pressure can “blow out” the pilot light, requiring it to be relit. It is preferred therefore that a fluid distribution system provide a predetermined pressure with minimum fluctuation for proper operation of the equipment attached thereto.
Many of the fluidic shut-off valves known in the art comprise a ball or a piston that is positions it self against a seat in response to sensing a difference in pressure across the valve between the upstream line and the downstream line. These valves operate in one of two positions, a nominal flow “on” position wherein fluid can flow through the valve, and an “off” state triggered by a pressure differential. When triggered into the “off” position, these valves are designed to completely prevent fluid flow through the valve.
One significant drawback of these conventional shut-off valves is that once they are triggered into an “off” state it is difficult to restore nominal fluid flow. For example, to restore flow through a gas shut-off valve, the gas line must be de-pressurized and the valves either replaced or manually reset. The time and labor required to restore fluid flow can be particularly costly when the valves are not easily accessible, such as when they are located in walls, ceilings, floors, or are submerged in water or buried beneath the soil.
The costs involved in restoring normal flow can be exorbitant, in particular when it is considered that these valves often get triggered into their “off” state without being subjected to a catastrophic event. Sudden pressure surges in fluid distribution systems such as gas pipelines are common. Pressure changes of sufficient magnitude may “trigger” a conventional shut-off valve into its closed (off) position. These valves, once triggered into an “off” state, must be either replaced or manually reset, depending on design, despite the lack of a significant, or catastrophic, event and even though there has been no damage or failure within the distribution system.
Accordingly, there is a need for a safety shut-off valve, also often referred to as a surge relief valve, safety valve, or shut-off valve, in which nominal fluid flow, in particular gaseous flow, can be more readily restored. The present invention satisfies that need, as well as others, and overcomes the deficiencies of previously developed safety valves.